The treatment options for patients with malignant lymphoma have been substantially enriched by the development of B-cell-specific monoclonal antibodies. One of the reasons for the attractiveness of this approach is the different mode of action of these antibodies compared to chemotherapy: they can exert tumor-suppressive effects by at least three major mechanisms: an intrinsic cytotoxic activity, antibody-dependent cellular cytotoxicity (ADCC), and activation of complement-dependent cytolysis (CDC). These monoclonal antibodies can be applied in an unconjugated form or as a carrier of cytotoxic drugs or radioisotopes. The chimeric anti-CD20 antibody rituximab has a direct anti-lymphoma activity, and is highly active in indolent and aggressive lymphoma, in particular in combination with chemotherapy. The anti-CD52 antibody alemtuzumab is effective in the treatment of patients with chronic lymphocytic leukemia (CLL). Another attractive approach is to link anti-CD20 antibodies to radioisotopes, thereby exploiting the radiosensitivity of malignant lymphomas: encouraging results were already presented for the yttrium-90-((90)Y-)labeled anti-CD20 antibody ibritumomab tiuxetan as well as for the iodine-131-((131)I-)labeled anti-CD20 antibody tositumomab.